Method of applying hot-melt glue

ABSTRACT

A method of applying hot-melt glue to an object consisting of the steps of heating a transfer bar to a temperature high enough to melt the glue, pressing said bar against solid hot-melt glue to coat said bar with a film of liquid glue, and pressing said bar against said object to transfer said glue thereto.

United States Patent Charles C. Krug 607 East 5th St., Summit, Mo. 64063781,545

Dec. 5, 1968 Dec. 21, 1971 lnventor Appl. No. Filed Patented METHOD OFAPPLYING HOT-MELT GLUE 7 Claims, 4 Drawing Figs.

11.8. C1 117/38, 117/12 0,118/202,118/243,118/263 1nl.Cl 844d 1/20, 844d1/02 Field of Search 101/426; 117/38,63, 121, 120; 118/263, 202,243;295/290, 291; 320/578 Primary ExaminerA1fred L. Leavitt AssistantExaminerEdward G. Whitby Attorney-John A. Hamilton ABSTRACT: A method ofapplying hot-melt glue to an object consisting of the steps of heating atransfer bar to a temperature high enough to melt the glue, pressingsaid bar against solid hot-melt glue to coat said bar with a film ofliquid glue, and pressing said bar against said object to transfer saidglue thereto.

METHOD OF APPLYING HOT-MELT GLUE This invention relates to new anduseful improvements in the application of glue, and has particularreference to a transfer method of applying hot-melt glue. The method ofthe present application can be used, for example, in applying inventorycontrol tickets to merchandise for sale, the tickets being removed asthe merchandise is sold and used to facilitate a continuous runninginventory of stock, and will be so described, although it will bereadily apparent that the invention has application generally in manyother usages.

Hot-melt glue has certain advantages in the above usages, as well asmany others, in that is requires no moisture to activate it, that isprovides a more secure attachment than other adhesives, and that itrequires very little pressure to make an adequately secure connection,thus making it well adapted for hurried or high-speed manual applicationof tickets where careful handling is not particularly possible, and forapplication of the tickets to soft, yieldable merchandise or merchandisepackages. The glue is ordinarily quite hard and solid at normal roomtemperatures, but is prepared for use in present methods by melting itto liquid form in a heated pot, from which it is applied to merchandisetickets or the like by dipping a brush or other applicator into the potand then daubing the glue on to the ticket, either manually or by somemechanical means. These methods are subject to several substantialdisadvantages. First, they require a substantial time period to melt thepot of glue, so that no apparatus dependent thereon can be readied foroperation in a conventionally short time. Second, the glue, or itsvolatile components, vaporize and pass ofi as fumes from the hot glue,with the result that the glue in the pot gradually solidifies andbecomes unusable when heated for extended periods, so that large amountsof glue are commonly wasted. Third, the fumes from the hot glue condenseand solidify on nearby objects, constituting a messy nuisance, and, ifthe applicator is a mechanical device, tending to foul the operation ofthe device so that it requires frequent and difficult cleaning. Fourth,it is difficult by these methods to apply glue solely to a predeterminedportion of an object in a predetermined pattern, so that if, forexample, the merchandise ticket consists of a base portion to be adheredand one or more perforated sections which may be torn off, the baseportion may be inadequately adhered and the perforated sections adhered.Fifth, it is difficult in these methods to regulate closely the amountof glue applied. A thin coat of glue makes the best bond, while a thickcoat will make a poorer bond, and excess glue may be squeezed out fromthe edges of the ticket when it is pressed into place.

Accordingly, the principal objects of the present invention are theprovision of a method of applying hot-melt glue which overcomes all ofthe above enumerated disadvantages of prior methods, in that it permitsthe use of apparatus which may be readied for use with extreme rapidity,which greatly reduces wastage of glue, which largely eliminates thefouling of nearby objects by glue vapor, which permits application ofglue in closely defined areas and patterns, and which permits closeregulation of thickness of the glue film applied.

To this end, the invention may be summarized as consisting of thesuccessive steps of first heating a transfer bar to a temperaturesufficiently high to melt said glue when applied to said glue in itsnormal solid form, said transfer bar having an applicator face of thearea and pattern in which it is desired to apply glue to an object, thenpressing said applicator face against said solid glue whereby the formeracquires a film of liquid glue, then pressing said applicator faceagainst said object to transfer said glue film to said object.

With these objects in view, as well as other objects which will appearin the course of the specification, reference will be had to theaccompanying drawings, wherein;

FIG. 1 is a diagrammatic view illustrating the various steps of theprocess of applying hot-melt glue embodying the present invention;

FIG. 2 is a view similar to FIG. 1, illustrating a slight modificationof the process,

FIG. 3 is an enlarged, fragmentary side elevational view of the transferbar shown in H6. 1, and

FIG. 4 is an enlarged face view of the applicator face of the transferbar shown in FIG. 1.

Like reference numerals apply to similar parts throughout the severalviews. The numeral 2 applies to a block of hot-melt glue, which it willbe understood is quite hard and solid at room temperature, carried by asuitable support 4. The numeral 6 applies to a merchandise inventorycontrol ticket or other object to which the glue is to be applied,carried by a suitable support 8. The numeral 10 applies to a transferbar, formed of metal or other suitable material, said transfer barhaving an applicator face 12 of a size and shape corresponding to thepattern of the glue it may be desired to apply to ticket 6. Saidapplicator face may, as shown, be divided into a larger number ofseparate areas 14 (see FIGS. 3 and 4) by grooves 16 formed in said face.It is usually important that said grooves be sufficiently wide that theyare not likely to become completely filled with residual glue remainingin the applicator face during performance of the process, and that saidgrooves be vented to the atmosphere through faces of the bar other thanthe applicator face, as shown.

The process forming the subject matter of the present inventioncomprises the following steps: First, transfer bar 10 is heated by anysuitable means, such as electric heater coil 18 surrounding said bar andconnected to a source of electrical power, to elevate applicator face 12thereof to a temperature sufficiently high to melt glue 2. Second,applicator face 12 of bar 10 is pressed momentarily against face of glueblock 2, as shown in position A of the transfer bar, whereby a smallamount of glue at the surface of said block is melted and adheres toface 12 as a liquid film. Third, applicator face 12 is pressed againstticket 6, or any other object to which it may be desired to apply glue,as shown at position B of the transfer bar, whereby to transfer the filmof glue to said ticket. The ticket is then ready for immediate use, andmust of course be adhered, before the glue cools and dries.

The process as thus far described has several advantages. The transferbar may be heated rapidly, much more rapidly than a pot of glue can bemelted, so that an apparatus utilizing the present method can be readiedfor use in a fraction of the time heretofore required. Substantiallyonly the amount of glue required for each application is melted at onetime, so that the entire supply of glue is not subject to vaporizationand consequent thickening by being kept constantly in a heated liquidstate. For the same reason, nearby machine parts or other objects arenot subject to be fouled by condensing glue vapor to any appreciableextent, and so do not require cleaning as frequently as before. The glueis applied to ticket 6 in an accurately controlled pattern, which may beimportant in many circumstances, for example, when a ticket may consistof two or more sections, some to be adhered and some not.

The process also permits close control of the amount of glue, orthickness of the glue film, applied to each ticket 6, it beingunderstood that a thin film of glue generally provides the best bond andis therefore to be desired. Primarily, this control is provided byregulation of the temperature of the transfer bar, as for example, bythermostatic control of heater coil 18. Generally, a higher bartemperature will melt the glue of block 2 to a more liquid state, withless surface tension, than a lower bar temperature, so that a thinnerfilm of glue adheres to the applicator face of said bar. Thus, theprocess may be said to include the initial step of regulating the bartemperature to provide a glue film of the desired thickness, and thistemperature may vary with the characteristics of the particular glueused. Secondarily, control of film thickness is provided by the grooves16 formed in the applicator face of the transfer bar. If the transferbar carries more glue than desirable to ticket 6, said grooves providezones or pockets into which the excess glue may escape as face 12 ispressed against ticket 6, so that at least portions of the glue area(those portions corresponding to areas 14 of face 12), will have a gluefilm of the desired thickness. The pressure with which face 12 ispressed against ticket 6 is also a determining factor affecting the filmthickness on these areas. In this connection, the formation of grooves16 of a size not likely to be completely clogged by residual glue, atleast in reasonably extended periods of use, and the venting thereof tothe atmosphere through bar surfaces other than face 12, is quiteimportant in that this prevents the buildup of air pressure in saidgrooves which would inhibit the flow of excess glue thereinto. Thesefeatures also have the additional function of admitting air over theglue film, tending to defeat the vacuum" which otherwise would tend tohold the ticket against face 12 as the transfer bar is lifted therefrom,even when the glue is quite fluid.

TI-Ie division of applicator face 12 into small areas 14 by grooves 16also has valuable functions even when only the optimum amount of glue ispicked up thereby from glue block 2. This optimum amount may be definedas just enough glue to coat areas 14, with no appreciable excess to besqueezed into the grooves when the transfer bar is pressed againstticket 6. Under these circumstances, grooves 16 have the functions of,first, providing passages for the circulation of air between the ticketand the object to which it is adhered after the ticket has been applied,thereby promoting faster drying of the glue, second of providingpassages for the escape of air which otherwise might be trapped betweenthe ticket and the object in the form of bubbles", in the area of whichthere would of course be no adhesion, and third of economizing in theamount of glue used, with no appreciable loss of bonding efficiency. Inthis connection, it will be noted that areas 14 may be of any desiredsize, and that if pick-up of only the optimum amount of glue by thetransfer bar can be maintained, areas 14 may be as small and closelyspaced as the projections" of a half-tone photographic printing plate.

The steps of the process thus far described, with relation to themovement of the transfer bar, could obviously be performed eithermanually, or by any suitable mechanical means, not shown. When performedby mechanical means in which transfer bar has a fixed path of movement,it will be necessary to feed the glue 2 so that it will always present ausable surface to the transfer bar, despite the fact that the body ofglue is gradually consumed. This may be done, for example, by elevatingglue support 4 gradually by automatic means or by transporting a tapecoated with glue across support 4, or other means. However, these areapparatus considerations not pertinent to the process concept claimed.When the process is performed by mechanical means, such as aself-contained mechanism to which solid hot-melt glue and tickets 6 arefed automatically, it may also be desirable that the process steps beperformed in a fixed cyclical sequence, such for example, that oneticket with glue properly applied thereto is delivered each time anoperating handle is pressed. That is, each time a cycle is initiated, itwill be completed, though not repeated until the operating handle isagain pressed. In connection with this type of operation, certainvariations of the process are pertinent. For example, as diagrammed inFIG. 1, transfer bar 10 may be provided with a neutral or rest positionas indicated at C in which it is not in engagement either with glueblock 2 or ticket 6. The cycle of movement of the transfer bar is firstfrom position C to position A, then to position B, and finally back torest at position C. This cycle has the advantage that any ticket 6 towhich glue has been applied is immediately available for use, which maybe important if, as is often the case, the tickets are numbered insequence, so that there may be virtually any time delay betweensuccessive cycles. How-- ever, if there are substantial time lapsesbetween cycles, residual glue on face 12 of the transfer bar mayvaporize, thicken and solidify, necessitating frequent cleaning. In FIG.2, the transfer bar also has a neutral position at which it comes torest after completion of each cycle, but this neutral position isidentical to position B, against ticket 6, so that the full cycle ofmovement consists of only two motions, first from from position B toposition A, then back to position B. In this cycle, the ticket 6 underthe applicator bar is of course not immediately available for use, butis has the advantage that the glue trapped between the transfer bar andthe ticket is largely shielded from the air, and hence remains fluid formuch longer periods than it would if exposed to air, as in FIG. 1, durintime lapses between successive cycles. Thus the cycle of FI 2 permitsmuch longer periods of time between successive cycles of operation, withgreatly reduced fouling of the transfer bar applicator face bysolidified residual glue.

While I have shown and described certain specific embodiments of myinvention process, it will be readily apparent that many minormodifications thereof could be made without departing from the spirit ofthe invention as defined by the scope of the appended claims.

What I claim as new and desire to protect by Letters Patent l. A processfor applying hot-melt glue to an object comprising the successive stepsof:

a. heating a transfer bar having a glue applicator face to a temperaturesufi'iciently high to melt said glue when pressed against hot-melt gluein its solid form,

b. moving said transfer bar relatively to a surface of solid, hot-meltglue to press the applicator face of said bar and said surface of solid,hot-melt glue together whereby said glue surface is melted and a portionthereof adheres to said applicator face as a liquid film, and

moving said applicator bar relatively to said object to press saidapplicator face and said object together, whereby said film of liquidglue is transferred to said object.

2. A process as recited in claim I for applying said glue to said objectin a predetermined area pattern, and including the additional initialstep of forming the applicator face of said transfer bar to correspondto the desired area pattern.

3. A process as recited in claim I with the additional initial step ofregulating the temperature of said transfer bar whereby to vary thethickness of the liquid glue film acquired by said applicator face formsaid surface of solid, hot-melt glue, higher bar temperatures reducingthe surface tension of said liquid glue and hence reducing the thicknessof said film.

4. A process as recited in claim 1 with the additional initial step ofdividing the applicator face of said transfer bar into smaller componentareas by forming grooves in said bar, said grooves opening through theapplicator face thereof.

5. A process as recited in claim 4 with the additional step of ventingsaid grooves to the atmosphere through surfaces of said applicator barother than the applicator face thereof.

6. A process as recited in claim 1 wherein the movements of saidtransfer bar relative to said glue surface and said object are performedin a fixed cyclic sequence, and wherein said transfer bar is providedwith a neutral position not in engagement either with said solidhot-melt glue or with said object, the sequential cycle of movement ofsaid transfer bar beginning and ending with said bar in said neutralposition.

7. A process as recited in claim I wherein the movements of saidtransfer bar relative to said glue surface and said object are performedin a fixed cyclical sequence, said cyclical sequence beginning andending with the applicator face of said transfer bar pressed againstsaid object.

2. A process as recited in claim 1 for applying said glue to said objectin a predetermined area pattern, and including the additional initialstep of forming the applicator face of said transfer bar to correspondto the desired area pattern.
 3. A process as recited in claim 1 with theadditional initial step of regulating the temperature of said transferbar wherEby to vary the thickness of the liquid glue film acquired bysaid applicator face form said surface of solid, hot-melt glue, higherbar temperatures reducing the surface tension of said liquid glue andhence reducing the thickness of said film.
 4. A process as recited inclaim 1 with the additional initial step of dividing the applicator faceof said transfer bar into smaller component areas by forming grooves insaid bar, said grooves opening through the applicator face thereof.
 5. Aprocess as recited in claim 4 with the additional step of venting saidgrooves to the atmosphere through surfaces of said applicator bar otherthan the applicator face thereof.
 6. A process as recited in claim 1wherein the movements of said transfer bar relative to said glue surfaceand said object are performed in a fixed cyclic sequence, and whereinsaid transfer bar is provided with a neutral position not in engagementeither with said solid hot-melt glue or with said object, the sequentialcycle of movement of said transfer bar beginning and ending with saidbar in said neutral position.
 7. A process as recited in claim 1 whereinthe movements of said transfer bar relative to said glue surface andsaid object are performed in a fixed cyclical sequence, said cyclicalsequence beginning and ending with the applicator face of said transferbar pressed against said object.